全文获取类型
收费全文 | 1025篇 |
免费 | 53篇 |
专业分类
电工技术 | 7篇 |
综合类 | 2篇 |
化学工业 | 216篇 |
金属工艺 | 30篇 |
机械仪表 | 22篇 |
建筑科学 | 54篇 |
矿业工程 | 2篇 |
能源动力 | 21篇 |
轻工业 | 160篇 |
水利工程 | 2篇 |
无线电 | 82篇 |
一般工业技术 | 207篇 |
冶金工业 | 84篇 |
原子能技术 | 10篇 |
自动化技术 | 179篇 |
出版年
2023年 | 20篇 |
2022年 | 18篇 |
2021年 | 23篇 |
2020年 | 20篇 |
2019年 | 21篇 |
2018年 | 16篇 |
2017年 | 20篇 |
2016年 | 35篇 |
2015年 | 19篇 |
2014年 | 40篇 |
2013年 | 50篇 |
2012年 | 42篇 |
2011年 | 54篇 |
2010年 | 70篇 |
2009年 | 59篇 |
2008年 | 54篇 |
2007年 | 56篇 |
2006年 | 28篇 |
2005年 | 33篇 |
2004年 | 37篇 |
2003年 | 26篇 |
2002年 | 14篇 |
2001年 | 17篇 |
2000年 | 19篇 |
1999年 | 20篇 |
1998年 | 18篇 |
1997年 | 19篇 |
1996年 | 17篇 |
1995年 | 5篇 |
1994年 | 9篇 |
1993年 | 9篇 |
1992年 | 15篇 |
1991年 | 15篇 |
1990年 | 13篇 |
1989年 | 7篇 |
1988年 | 12篇 |
1987年 | 12篇 |
1986年 | 10篇 |
1983年 | 7篇 |
1982年 | 12篇 |
1981年 | 7篇 |
1980年 | 10篇 |
1979年 | 8篇 |
1978年 | 8篇 |
1977年 | 6篇 |
1976年 | 7篇 |
1974年 | 11篇 |
1973年 | 4篇 |
1972年 | 5篇 |
1966年 | 3篇 |
排序方式: 共有1078条查询结果,搜索用时 15 毫秒
51.
Gabriel Maria Ingo Cristina Riccucci Gianni Chiozzini 《Journal of the American Ceramic Society》2001,84(8):1839-1843
The origin of gas-porosity in gold-based alloys produced via lost-wax casting in CaSO4 -bonded investment has been identified using a combination of microanalytical and thermal techniques. The occurrence of gas-porosity is related to the thermal decomposition of CaSO4 , which, with SiO2 , constitutes the investment material and decomposes at a temperature very close to the casting temperature of some typical gold alloys used for jewelry production. The thermal reaction generates SO2 , leading to gas-porosity and, therefore, to defective products. Furthermore, the results show the detrimental effect of thermal decomposition caused by the presence of ZnO, Cu2 O, CuO, NiO, and Ag2 O formed on the surface of the gold-based alloy during air melting or casting. Therefore, the solid-state thermal decomposition of CaSO4 in the presence of other ceramic oxides has been investigated and found to be related to their surface acid–base properties, measured as isoelectric points on the solid surface. 相似文献
52.
53.
Mirco Wegener Luckman Muhmood Shouyi Sun Alex V. Deev 《American Institute of Chemical Engineers》2014,60(9):3350-3361
The experiments on the capillary breakup of slag jets at high temperatures are presented in this article. The impact of external excitations on the disintegration process was investigated in a furnace with optical access filmed at frame rates up to 10,000 fps. A synthetic calcia‐alumina slag was used to form jets at different temperatures (1570–1660°C) and jet velocities (0.6–1.4 ms?1). The impact of external vibration on the breakup was evident: for low jet velocities, the jet length decreased, the droplet size increased, satellite droplet formation was hindered, and a distinct “pumping mechanism” was observed. For jets with higher velocity, the jet length decreased by 30%, the droplet generation frequency increased from 20 to 250 droplets per second, the drop sizes were uniform, and satellite formation was also suppressed. In this case, the ideal case in which the volume of one wave instability forms one droplet was achieved. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3350–3361, 2014 相似文献
54.
Jan Hcker Tevfik Onur Mente Alessandro Sala Andrea Locatelli Thomas Schmidt Jens Falta Sanjaya D. Senanayake Jan Ingo Flege 《Advanced Materials Interfaces》2015,2(18)
The interaction of molecular hydrogen with ceria is of important relevance for heterogeneous catalysis related to green chemistry and renewable energy. Here, the complex structural transformations of a well‐defined cerium oxide model catalyst are followed in situ and in real time when exposed to a reactive H2 environment. By using electron spectromicroscopy and diffraction with chemical and structural sensitivities, it is demonstrated that the transition from CeO2 to crystalline Ce2O3 occurs through a mixture of transient, coexisting phases on the nanoscale. The findings establish a clear relationship between structure and functionality for hydrogen dissociation over ceria(111), bearing profound implications on the nature of the reduction (Ce4+ → Ce3+) and mechanism for H2 scission. 相似文献
55.
Manfred Schulz Gerd West Sakum Ourk Ingo Strunz 《Advanced Synthesis \u0026amp; Catalysis》1980,322(2):295-304
Azoperoxides. VI. Selective Decomposition of β-Azoacylperoxides The selective decomposition of the O O-Groups in the azoperoxides 1 and 2 is possible by reaction with dimethylaniline at 35°C. Rate constants were measured and the decomposition products were analyzed. Intermediates are azoalkyl radicals. The radical yield of the amine induced decomposition of 2 in ethylbenzene is 8.2% at 35°C. UV irradiation of the azoperoxides 1 and 2 at 20°C in ethylbenzene results in a quantitative and selective decomposition of the azo groups. Intermediates are C-radicals with intact peroxide groups. The reaction of 1 and 2 with triethylstannane yields reduction products of the O O-groups and the NN-groups, respectively. 相似文献
56.
Florenza Lüder Ripoli Annika Mohr Susanne Conradine Hammer Saskia Willenbrock Marion Hewicker-Trautwein Silvia Hennecke Hugo Murua Escobar Ingo Nolte 《International journal of molecular sciences》2016,17(5)
Mammary neoplasms are the tumors most affecting female dogs and women. Formalin-fixed, paraffin-embedded (FFPE) tissues are an invaluable source of archived biological material. Fresh frozen (FF) tissue is considered ideal for gene expression analysis. However, strategies based on FFPE material offer several advantages. Branched-DNA assays permit a reliable and fast workflow when analyzing gene expression. The aim of this study was to assess the comparability of the branched-DNA assay when analyzing certain gene expression patterns between FF and FFPE samples in canine mammary tumors. RNA was isolated from 109 FFPE samples and from 93 FF samples of different canine mammary tissues. Sixteen (16) target genes (Tp53; Myc; HMGA1; Pik3ca; Mcl1; MAPK3; FOXO3; PTEN; GATA4; PFDN5; HMGB1; MAPK1; BRCA2; BRCA1; HMGA2; and Her2) were analyzed via branched-DNA assay (b-DNA). ACTB, GAPDH, and HPRT1 were used as data normalizers. Overall, the relative gene expression of the two different origins of samples showed an agreement of 63%. Still, care should be taken, as FFPE specimens showed lower expression of the analyzed targets when compared to FF samples. The fact that the gene expression in FFPE proved to be lower than in FF specimens is likely to have been caused by the effect of storage time. ACTB had the best performance as a data normalizer. 相似文献
57.
O. A. Charl G. Czymek B. Giesen M. Sauer L. Scheibl J. Schruff R. Schick A. Panin A. John S. Jung K. Rummel L. Wegener 《Fusion Engineering and Design》2009,84(7-11):1416-1419
Forschungszentrum Jülich has taken over the design, manufacturing and assembly of the superconducting busbar system for the stellarator Wendelstein 7-X. This includes the busbars itself, the support structure consisting of supports and clamps, and the joints for electrical and hydraulic connection of the busbars and coil terminals. Apart from providing the required electrical connection scheme, the busbar system has to be designed for relevant electrical and mechanical loads. Numerous interfaces and geometric boundary conditions define the confined space to accommodate the busbars and their support elements. This article describes how the individual challenges to engineering have been met in the course of the project. This includes design concepts and the method for iterative design of supports with respect to the individual load distribution caused by the supports itself. 相似文献
58.
K. Heinke Schlünzen David Grawe Ingo Schlüter 《Journal of Wind Engineering & Industrial Aerodynamics》2011,99(4):217-225
Obstacles considerably influence boundary layer processes. Their influences have been included in mesoscale models (MeM) for a long time. Methods used to parameterise obstacle effects in a MeM are summarised in this paper using results of the mesoscale model METRAS as examples. Besides the parameterisation of obstacle influences it is also possible to use a joint modelling approach to describe obstacle induced and mesoscale changes. Three different methods may be used for joint modelling approaches: The first method is a time-slice approach, where steady basic state profiles are used in an obstacle resolving microscale model (MiM, example model MITRAS) and diurnal cycles are derived by joining steady-state MITRAS results. The second joint modelling approach is one-way nesting, where the MeM results are used to initialise the MiM and to drive the boundary values of the MiM dependent on time. The third joint modelling approach is to apply multi-scale models or two-way nesting approaches, which include feedbacks from the MiM to the MeM. The advantages and disadvantages of the different approaches and remaining problems with joint Reynolds-averaged Navier-Stokes modelling approaches are summarised in the paper. 相似文献
59.
The residual strength of a flat panel (thickness 7.6 mm) with five stringers, machined from a monolithic block of Al2024-T351 material, which contained a crack that divided the central stringer, was to be predicted during a Round Robin organised by ASTM. The initial crack tips were right ahead of the stringers #2 and #4, respectively, so that crack branching along the skin and into the stringers occurred after initiation. The prediction has been achieved using finite element simulations including crack extension, for which a cohesive model was utilised. Conventional material properties, yield and ultimate strength as well as experimental results from M(T) specimens in terms of force, COD and Δa, were given. The residual strength prediction was performed in two-steps: First the crack extension parameters for the cohesive model, the cohesive strength, T0, and the cohesive energy, Γ0, were determined by numerical reproduction of the results of the M(T) specimen. With the optimised parameters, the five-stringer panel was modelled. These steps were conducted by two different finite element models: by a shell and a 3D finite element mesh. It turned out that it is possible to analyse the structure with both models. In the 3D case, the residual strength prediction was conservative and the deviation of the predicted from the experimental value was below 9%. The results of the shell simulation were even closer to the experiment (deviation approximately 3%), but the simulation was non-conservative. 相似文献
60.
Marc Blumenau Afrooz Barnoush Ingo Thomas Harald Hofmann Horst Vehoff 《Surface & coatings technology》2011,205(2-3):542-552
The present study discusses the impact of selective oxidation during in-line annealing of Fe–23%Mn–0.6%C–0.3%Si steel on surface and sub-surface properties and is focused on hot-dip galvanizability and susceptibility to hydrogen-induced delayed cracking. Annealing temperature (700–1100 °C) and dewpoint DP (? 15/?30/?50 °C) of the 5%H2–N2 annealing atmosphere were varied in order to investigate Zn wetting in dependence on selective oxidation of Mn and Si. Sub-surface microplasticity (hardness, pop-in frequency, pop-in activation load) was examined by electrochemical nanoindentation in-situ to hydrogen charging (ECNI) to assess hydrogen/material interactions. Zn wetting fails if external Mn and Si oxidation is not avoided by performing high reductive bright annealing (1100 °C/DP ? 50 °C). Zn wetting will however turn to increase if a roughly globular MnO layer appears and Si is internally oxidized (700–900 °C/DP ? 15 °C). Selective oxidation further affects hydrogen/material interactions by influencing the local distribution of solid-soluted Mn: ECNI results indicate hydrogen-induced dislocation demobilization (HEDE mechanism) or dislocation mobilization (HELP mechanism) in dependence on the local amount of solid-soluted Mn within the sub-surface. Macroscopic delayed cracking seems to occur earlier if HELP is predominating. The gained results benefit understanding the impact of selective oxidation on galvanizability and susceptibility to hydrogen-induced failure of austenitic FeMnC steel and advance further developments in processing high Mn alloyed steels. 相似文献